Why not use rubbing alcohol for spot spraying of equipment? Seems cheaper and there is no need to mix a specific ratio for a spray bottle.
Because isopropyl alcohol isn’t for human consumption, you could use some Vodka. I think StarSan would prove to be one of the least expensive solutions.
I use SS, just asking.
While it’s an excellent sanitizer, regardless if it’s denatured ethyl or isopropyl alcohol, it’s very toxic to drink. However, when applied topically (i.e. on skin before a shot, or as an equipment sanitizer…), it evaporates. Unfortunately, what is used to denature it does leave behind some undesirable residue in very minute amounts.
I use it to sanitize the mouth of a flask for yeast starters, cleaning surfaces where I do yeast work, and such, not with with anything that contacts my beer.
If you wanted to use alcohol, 151 proof spirits would be the ideal choice. Cheap vodka is only 40% alcohol and isn’t effective as 70%.
Everclear
Isopropyl alcohol and a flame is what I use to sanitize all my brewing/lab equipment. Cheaper and more effective than chemical sanitizers. The flame is key, though.